Abstract: A post driver assembly for driving square wood posts comprising a grip retainer plate having a rectangular plate hole centrally located in the plate which is oversized compared to an outside dimension of a square post. A post driver wedge is provided with a flat side for flush engagement with a post side when the post driver wedge is telescoped through the rectangular plate hole. The post driver wedge has a tapered side opposite to the flat side slidingly engageable with an edge of the rectangular plate hole for ensuring snug engagement of the flat side against the post. A screw is threaded through the wedge for attaching the wedge to the post to anchor the wedge to resist vertical slippage of the wedge relative to the wooden post.